Effective Population Size

Question 1

Ne

Answer 1

Effective Population Size

Question 2

Lekking species

Answer 2

has a popula0on that is “effectively” smaller, with regard to gene0cs.

Question 3

Effective population size

Answer 3

represents population’s risk from
genetic factors and its ability to
maintain evolutionary potential.

Question 4

Census population size

Answer 4

represents populations demographic
potential. Its number of
individuals.

Question 5

Factors Influencing Genetic

Properties of Populations

Answer 5

*Unequal breeding opportunities among
individuals.
•  Unequal family sizes.
•  Overlapping generations.
•  Natural selection against certain traits.
•  Unstable population sizes.

Question 6

Sewall Wright came up with the idea of

Answer 6

effec0ve popula0on size. In doing so, he was
able to create a metric that could be used to
standardize gene0c evalua0ons across
popula0ons and species

Question 7

Idealize popula0on

Answer 7

he asked
what size ideal popula0on would behave
similarly to the popula0on of interest.

Question 8

Five Characteristics

of an Characteristics

Answer 8

1. Equal sex ratios
2. Random mating
3. Descrete (non-overlapping) generations
4. ) Random Variation or equal reproductive sucess (no Selection)
5. Stable over across time

Question 9

Effective Population Size - Ne

Answer 9

THE SIZE OF AN 
IDEALIZED POPULATON 
THAT BEHAVES SIMILARLY 
TO THE POPULATION OF 
INTEREST WITH REGARD TO 
GENETICS

Question 10

Effective Population Size Metrics- Ne

Answer 10

– actual estimate of the effective
population size, or the census size of
an idealized population that would
move genes similarly

Question 11

Ne /N –

Answer 11

the ratio of the size of the
effective population size and the
census population size.

Question 12

Ne Estimators – Demographic

Methods

Answer 12

•  Demographic equations based 
on population characteristics.
Sex Ratios 
– Inbreeding 
– Variance 
– Spatially structured populations 
– Overlapping generations 
– Others!

Question 13

Ne Estimators – Unequal Sex Ratios

Answer 13

Populations with 
unequal sex 
ratios have 
reduced Ne/N 
ratios.

Question 14

Ne Estimators – variance in offspring

numbers

Answer 14

Ne/N ratio 
declines as 
variance in 
family size 
goes up.

Question 15

Ne Estimators – Inbreeding

Answer 15

Effective 
population size 
of inbreeding. 
-Note that the 
graph shows the 
effect of both 
variance and 
inbreeding.

Question 16

Ne Estimators – Fluctuations in

Population Size

Answer 16

The long-term Ne can be
reduced by fluctuations in
population size.

Question 17

Ne Estimators – Combinations of Factors

Answer 17

All of the demographic factors described
above can be combined into a single
equation to predict Ne for a species.

Question 18

Ne Estimators – Genetic Methods

Answer 18

based on observed 
genetic characteristics of the 
population. 
•  Estimate current Ne 
•  Estimate long-term/historical Ne 
•  Estimate population bottlenecks

Question 19

Conservation Uses of Effective

Population Size

Answer 19

Captive breeding populations
•  Reintroduction population sizes
•  Estimates of minimum viable populations
•  Estimates of viability of remnant populations
•  Determination of need for management actions

Question 20

Genetically Viable Population

Answer 20

– Early estimates of 50 individuals
50 does not preserve all diversity, so it
is a somewhat arbitrary figure

Question 21

Viable Population – Long Term

Answer 21

Estimates of 500 individuals 
500 does not preserve all diversity, so it is 
a somewhat arbitrary figure 
v  500 does not preserve “Evolutionary 
Potential”

Question 22

Not all individuals pass along genes, so

Answer 22

Ne is smaller than N.

Question 23

Multiple ways to calculate

Answer 23

Ne

Question 24

Variation in family size, overlapping

generations, and population fluctuation ….

Answer 24

greatly affect Ne

Question 25

50-500-5000 rule

Answer 25

is somewhat arbitrary

and matter of debate.

Question 26

Ne for most populations is

Answer 26

~0.1